Structural modifications in titania-doped tantalum pentoxide crystals: a Raman scattering study

Tantalum pentoxide (Ta2O5) is promising for coating and piezoelectric appli cations and has been considered as the dielectric gate material for the nex t generation of memory devices. In this work, TiO2-doped Ta2O5 crystals wer e prepared using the laser-heated pedestal growth technique, as grown speci mens were found to crystallize in monoclinic phase at room temperature. The structural modifications in these crystals resulting from variation of TiO 2 composition (0-11%) and temperature (-248-900 degreesC) were studied usin g Raman spectroscopy. The low frequency external modes (upsilon < 100 cm(-1 )) that originate from the interaction between TaOn5-2 eta/Ta6O12+6 cluster s/polyhedra exhibit a strong compositional and temperature dependence in te rms of their intensity and frequency variations. The Raman spectral evoluti ons suggested a monoclinic to orthorhombic structural phase transition at a bout 327, 397, 487, and 577 degreesC For 0, 5, 8, and 11% TiO2-doped Ta2O5, respectively. (C) 2001 Elsevier Science Ltd. All lights reserved.